1. Field of the Invention
The invention relates to a method of and a device for determining a position of a solidification point in a strand during a continuous casting of liquid metals, in particular liquid steel, in which a strand formed in a continuous casting mold as a billet, ingot, bloom, preliminary section, thin slab, or slab strand, is displaced in support roller segments, is cooled, and is drawn out by support roller segments with driven support roller pairs. During production of above-mentioned elongate products with a continuous casting method, the cast initial material should meet high requirements with respect to its inner quality. Of large importance is as uniform as possible distribution of alloy elements over the entire strand cross-section, without a damaging segregation that may occur in the strand center and in inner cracks.
2. Description of the Prior Art
Known is an electromagnetic stirring process in which a strand stirrer operates in the region of final solidification, and the time at which the desired action of the stirrer should reach the core melt, depends on the position of the solidification point. Because the solidification point is not known or is uncertain, in all cases, displacement of the device in the strand displacement direction is necessary.
Also known is a so-called soft-reduction process in which the strand thickness is reduced in the region of final solidification to thereby press back residual melt enriched with alloy elements. The known method aims at circulating or distribution of the core melt.
It is, therefore, necessary to be able to determine the solidification point length as precisely as possible. To this end, a calculation model was developed based on relevant data such as, e.g., casting speed, amount of cooling water, kind of steel, or steel entry temperature.
The precision of the calculation model depends on the reliability of the available process data and on the influence of non-model-forming process parameters. To this, changes in physical characteristics of the strand or other process variables should be taken into account. Thus, elasto-plastic behavior of a completely solidified strand differs from that of only partially solidified strand. Also are available other methods of determining the degree of solidification such as, e.g., determining the force of drawing out the strand through the support roller system of a continuous casting machine, and measuring the support force at segment or driven rollers (EP 1197007 A1).
The object of the invention is to achieve a determination of the position of the solidification point in a strand more precise than with all of other known methods.